Methods and Systems for TDD PUCCH HARQ Resource Allocation for Enhanced Physical Downlink Control Channel (EPDCCH)

ABSTRACT

PUCCH resource determination for HARQ-ACK transmission in response to ePDCCH-scheduled PDSCH or ePDCCH-indicated SPS release in a TDD radio communication system. Downlink control information (DCI) is received in a downlink subframe via an Enhanced Physical Downlink Control Channel (ePDCCH). A resource index for a Physical Uplink Control Channel (PUCCH) resource is determined, based on the lowest enhanced Control Channel Element (eCCE) index of the received DCI, a device-specific offset value, and an index i that identifies the downlink subframe in a pre-determined set of one or more downlink subframes associated with an uplink subframe. The PUCCH resource is determined according to a formula that results in a sequential allocation of PUCCH resources in the uplink subframe with respect to the downlink subframes associated with the uplink subframe, for each of a plurality of sets of ePDCCH resources. HARQ feedback is transmitted in the uplink subframe, in the indexed PUCCH resource.

TECHNICAL FIELD

The present invention generally relates to wireless communicationnetworks, and particularly relates to the allocation of uplink controlchannel resources within such networks.

BACKGROUND

The 3rd-Generation Partnership Project (3GPP) has developedspecifications for a fourth-generation wireless communicationstechnology known as “Long Term Evolution,” or “LTE.” LTE uses OrthogonalFrequency Division Multiplexing (OFDM) in the downlink and DFT-spreadOFDM in the uplink, where DFT denotes “Discrete Fourier Transform”. Thebasic LTE physical resources can thus be seen as a time-frequency grid,as illustrated in FIG. 1, where each resource element corresponds to onesubcarrier during one OFDM symbol interval on a particular antenna port.An antenna port is defined such that the channel over which a symbol onthe antenna port is conveyed can be inferred from the channel over whichanother symbol on the same antenna port is conveyed. There is oneresource grid per antenna port.

In the time domain, LTE downlink transmissions are organized into radioframes of ten milliseconds. Each radio frame includes ten equally sizedsubframes of one millisecond. FIG. 2 illustrates this arrangement—onesees from the diagram that each subframe is divided into two slots, witheach slot having a duration of 0.5 milliseconds.

Resource allocation in LTE is described in terms of “Physical ResourceBlocks,” or “PRBs.” As shown in FIG. 3, a PRB corresponds to one slot inthe time domain and twelve contiguous 15-kHz subcarriers in thefrequency domain. The bandwidth, N_(BW), of the overall systemdetermines the number of PRBs in each slot, and each PRB spans six orseven OFDM symbols, depending upon the length of the cyclic prefix (CP)used. Two consecutive PRBs in time represent a PRB pair. User schedulingby the LTE base station, referred to as an “eNodeB” or “eNB”, isgenerally performed using the PRB pair as the smallest unit of resourceallocation.

Transmissions in LTE are dynamically scheduled based on transmittingdownlink assignments and uplink grants to targeted mobile terminals(referred to as “user equipment,” or “UEs,” in 3GPP terminology).According to Release 8 of the 3GPP standards, which was the firstrelease to include specifications for LTE, the downlink assignments anduplink grants are transmitted in a defined control region using PhysicalDownlink Control Channels (PDCCHs) targeted to specific UEs. The searchspace for PDCCH reception, which defines those resources in any givensubframe that might include control information for the UEs, is known tothe UEs. The UEs thus blindly decode those portions of the receivedsignal to find PDCCHs targeted to them.

More broadly, PDCCHs are used to convey UE-specific schedulingassignments for the downlink and uplink grants, as noted, and arefurther used for Physical Random Access Channel (PRACH) responses,uplink power control commands, and common scheduling assignments forsignaling messages that include, among other things, system informationand paging.

FIG. 4 illustrates that a “normal” downlink subframe includes a controlregion at the beginning of the subframe, followed by a data region. Thesize of the control region in which PDCCHs are transmitted can vary insize from one to four OFDM symbols in dependence on the involvedconfiguration. A Physical Control Format Indicator (PCFICH) is used toindicate the control region length and is transmitted within the controlregion at locations known by the UEs. A UE thus learns the size of thecontrol region in a given downlink subframe by decoding the PCFICHtransmitted in that subframe, and therefore knows in which OFDM symbolthe data transmission starts.

PDCCHs are made up of Control Channel Elements (CCEs), where each CCEconsists of nine Resource Element Groups (REGs). Each REG in turnconsists of four resource elements (REs). LTE defines four PDCCH formats0-3, which use aggregation levels of 1, 2, 4, and 8 CCEs, respectively.Given the modulation format used for PDCCH transmission, two bits can betransmitted on each individual RE aggregated within a PDCCH; with 1CCE=9 REGs=36 REs and 2 bits/symbol, one can transmit 72 bits via aformat 0 PDCCH, 144 bits via a format 1 PDCCH, etc. As noted, PDCCHs aretransmitted in the defined control region—the first 1-4 symbols—of anygiven downlink subframe and extend over substantially the entire systembandwidth. Thus, the size of the control region in the given downlinksubframe and the overall system bandwidth define the number of overallCCEs available for PDCCH transmission.

FIG. 4 also illustrates the presence of Cell-specific Reference Symbols(CRS) within the downlink subframe. The locations and values of CRS areknown by the UEs, which use the received CRS for estimation of the radiochannel. The channel estimates are in turn used in the demodulation ofdata by the UEs. CRS are also used for mobility measurements performedby the UEs.

Because the CRS are common to all UEs in a cell, the transmission of CRScannot be easily adapted to suit the needs of a particular UE.Therefore, LTE also supports UE-specific reference symbols generallyintended only for assisting channel estimation for demodulationpurposes. These UE-specific RS are referred to as Demodulation ReferenceSymbols (DMRS). DMRS for a particular UE are placed in the data regionof the downlink subframe, as part of Physical Downlink Shared Channel(PDSCH) transmissions.

Release 11 of the 3GPP standards introduced the enhanced PDCCH (ePDCCH)as an additional, and more flexible, channel for transmitting controlmessages to UEs. An ePDCCH uses resources in the data region associatedwith PDSCH transmissions, rather than resource elements within thedefined control region at the beginning of the subframe. See “UniversalMobile Telecommunications System (UMTS); Technical Specifications andTechnical Reports for a UTRAN-based 3GPP system”, 3GPP TS 21.101,v.11.0.0.

FIG. 5 provides a basic illustration of PRB pairs allocated from thedata region of a downlink subframe, for use in the transmission of givenePDCCHs. The remaining PRB pairs in the data portion of the subframe canbe used for PDSCH transmissions; hence the ePDCCH transmissions arefrequency multiplexed with PDSCH transmissions. That arrangement differsfrom PDCCH transmissions, which are time multiplexed with respect toPDSCH transmissions—i.e., PDCCH transmissions occur only in the controlportion of the downlink subframe, which occurs in time before the dataportion in which PDSCH transmissions are performed.

Resource allocation for PDSCH transmissions can be according to severalresource allocation types, depending on the downlink control information(DCI) format. Some resource allocation types have a minimum schedulinggranularity of a resource block group (RBG). An RBG is a set of adjacent(in frequency) resource blocks. When scheduling the UE according tothese resource allocation types, the UE is allocated resources in termsof RBGs, rather than according to individual resource blocks (RBs) or RBpairs.

When a UE is scheduled in the downlink from an ePDCCH, the UE shallassume that the PRB pairs carrying the downlink assignment are excludedfrom the resource allocation, i.e., rate matching applies. For example,if a UE is scheduled to receive PDSCH in a certain RBG that consists ofthree adjacent PRB pairs, and if one of these PRB pairs contains thedownlink assignment, then the UE shall assume that the PDSCH istransmitted in only the two remaining PRB pairs in this RBG. Notably,Release 11 does not support multiplexing of PDSCH and ePDCCHtransmission within the same PRB pair.

ePDCCH messages are made up of enhanced Control Channel Elements(eCCEs), which are analogous to the CCEs used in the PDCCH. For purposesof mapping ePDCCH messages to PRB pairs, each PRB pair is divided intosixteen enhanced resource element groups (eREGs). Each eCCE is made upof four or eight of these eREGs, for normal and extended cyclic prefix,respectively. An ePDCCH is consequently mapped to a multiple of eitherfour or eight eREGs, depending on the aggregation level. The eREGsbelonging to a particular ePDCCH resides in either a single PRB pair (asis typical for localized transmission) or a multiple of PRB pairs (as istypical for distributed transmission).

One example of the possible division of a PRB pair into eREGs isillustrated in FIG. 6, which illustrates an unconstrained subframe. Eachblock or tile in the figure is an individual resource element (RE) andthe tile number corresponds to the EREG that the RE is grouped within.For example, tiles having the dotted background all belong to same EREGindexed at 0.

A UE can be configured so that multiple sets of PRB pairs are availablefor use as ePDCCH resources. Each ePDCCH resource set consists of N=2,4, or 8 PRB pairs. In addition, two modes of ePDCCH transmission aresupported, i.e., localized and distributed ePDCCH transmission. Each setof ePDCCH resources is independently configured as being of localized ordistributed type. In distributed transmission, an ePDCCH is mapped toresource elements in an ePDCCH set in a distributed manner, i.e., usingmultiple PRB pairs that are separated from each other in frequency. Inthis way, frequency diversity can be achieved for the ePDCCH message. Asof Release 11, the ePDCCH can be mapped to resource elements in up to DPRB pairs, where D=2, 4, or 8 (the value of D=16 is also beingconsidered in 3GPP). FIG. 7A illustrates an example of distributedtransmission, where D=4 is illustrated. As seen in the example, theePDCCH is divided into four parts, which are mapped to different PRBpairs. These four parts may correspond to eCCEs, for example.

In a localized transmission, on the other hand, an ePDCCH is mapped toone PRB pair only, if the space allows. Mapping to a single PRB pair isalways possible for aggregation levels one and two, and is possible alsofor aggregation level four for the case of a normal, “unconstrained”subframe and a normal CP length. Here, an “unconstrained” or normalsubframe is one having a PDSCH region that is not abbreviated.Constrained subframes include “special” subframes in TDD LTE thatinclude uplink and downlink portions, and subframes that are given overto another purpose, such as Multicast-Broadcast Single Frequency Network(MBSFN) transmissions. The number of eCCEs that fit into one PRB pair isgiven by Table 1, below. Thus, for example, in a normal subframe with anormal CP length, localized transmission using aggregation levels of 1,2, or 4 uses only a single PRB pair, while localized transmission usingan aggregation level of 8 requires the use of two PRB pairs.

TABLE 1 Number of eCCEs per PRB pair in localized transmission Normalcyclic prefix Extended cyclic prefix Special Special Special subframe,subframe, subframe, Normal configuration configuration Normalconfiguration subframe 3, 4, 8 1, 2, 6, 7, 9 subframe 1, 2, 3, 5, 6 4 2

In case the aggregation level of the ePDCCH is too large, a second PRBpair is used as well, and so on, using more PRB pairs, until all eCCEsbelonging to the ePDCCH have been mapped. FIG. 7B illustrates an exampleof localized transmission. In this example, the same four parts of theePDCCH are mapped to a single PRB pair.

As described above, certain downlink resources are made available forsending PDCCH and ePDCCH messages to the UE. However, a given UE is nottargeted to receive control channel messages in every subframe. Further,the UE does not know in advance precisely where a control channelmessage will be located among the resources made available for thecontrol channel messages. Thus, the UE must search for a control messagethat may not exist, in each of several possible locations for themessage. The concept of a “search space” is used to define a range ofpossible locations for control messages, to keep the required amount ofsearching to a reasonable level.

For the PDCCH, Release 8 of the 3GPP specifications for LTE define asearch space S_(k) ^((L)) for each of the possible aggregation levelsL∈{1,2,4,8} This search space is defined by a contiguous set of CCEsgiven by the following:

(Z _(k) ^((L)) +i)mod N _(CCE,k)  (1)

where N_(CCE,k) is the total number of CCEs in the control region ofsubframe k, Z_(k) ^((L)) defines the start of the search space. i is anindex value that ranges according to i=0, 1, . . . , M^((L))·L−1, whereM^((L)) is a pre-determined number of PDCCHs to monitor in the givensearch space, which depends on the aggregation level. Table 2, which isreproduced from Table 9.1.1-1 of 3GPP TS 36.213, “Physical LayerProcedures (Release 8),” provides the values of M^((L)) for each of thepossible aggregation levels L. Each CCE contains 36 QPSK modulationsymbols.

TABLE 2 M^((L)) vs. Aggregation Level L for PDCCH Search space S_(k)^((L)) Aggregation Number of PDCCH Type level L Size [in CCEs]candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 16 2 Common 4 16 4 816 2

It should be noted that with this definition, search space for differentaggregation levels may overlap with each other, regardless of systembandwidth. More specifically, UE-specific search space and common searchspace might overlap and the search spaces for different aggregationlevels might overlap. One example is shown below, in Table 3, wherethere are nine CCEs in total and very frequent overlap between PDCCHcandidates.

TABLE 3 N_(CCE, k) = 9, Z_(k) ^((L)) = {1, 6, 4, 0} for L = {1, 2, 4,8}, respectively. Search space S_(k) ^((L)) Aggregation PDCCH candidatesin Type Level L terms of CCE index UE-Specific 1 {1}, {2}, {3}, {4},{5}, {6} 2 {6, 7}, {8, 0}, {1, 2}, {3, 4}, {5, 6}, {7, 8} 4 {4, 5, 6,7}, {8, 0, 1, 2} 8 {0, 1, 2, 3, 4, 5, 6, 7}, {8, 0, 1, 2, 3, 4, 5, 6}Common 4 {0, 1, 2, 3}, {4, 5, 6, 7}, {8, 0, 1, 2}, {3, 4, 5, 6} 8 {0, 1,2, 3, 4, 5, 6, 7}, {8, 0, 1, 2, 3, 4, 5, 6}

As is also the case for PDCCH, the ePDCCH is transmitted over radioresources shared by multiple UEs. The enhanced CCE (eCCE) is introducedas the equivalent of the CCE for PDCCH. Like a CCE, an eCCE also has afixed number of resource elements. However, the number of resourceelements actually available for ePDCCH mapping is generally fewer thanthe fixed number, because many resource elements are occupied by othersignals such as Cell-specific Reference Signals (CRS) and Channel StateInformation-Reference Signal (CSI-RS). Code-chain rate matching isapplied whenever a resource element belonging to an eCCE contains othercolliding signals such as the CRS, CSI-RS, legacy control region or incase of Time Division Duplexing (TDD), the Guard Period (GP) and UplinkPilot Time Slot (UpPTS).

Consider the example in FIG. 8, where item 40 illustrates the PDCCHmapping. The PDCCH always avoids the CRS, so that a CCE always containsT_(avail)=36 available resource elements. In item 42, on the other hand,it is shown how an eCCE contains 36 resource elements nominally, but thenumber of available resource elements is reduced in the event that thereare colliding signals. Hence, T_(avail)≤36 resource elements for ePDCCH.Since the colliding signals are subframe dependent, the value ofT_(avail) becomes subframe dependent as well, and could even bedifferent for different eCCEs, if the collisions impact on the eCCEsunevenly. It is noted that when the number of eCCEs per PRB pair is two(see Table 1), the nominal number of resource elements per eCCE is not36, but instead is either 72 (for normal CP length) or 64 (for extendedCP length).

As of Release 11 of the 3GPP standards for LTE, the ePDCCH supports onlythe UE-specific search space, whereas the common search space remains tobe monitored in the PDCCH in the same subframe. In future releases, thecommon search space may be introduced also for ePDCCH transmission. TheRelease 11 standards specify that the UE monitors eCCE aggregationlevels 1, 2, 4, 8, 16 and 32, with restrictions shown in Table 4 below,where n_(EPDCCH) is the number of available resource elements for ePDCCHtransmission in a PRB pair. In Table 4, distributed and localizedtransmission refers to the ePDCCH mapping to resource elements.

TABLE 4 Aggregation levels for ePDCCH Aggregation levels Normalsubframes and special subframes, configuration 3, 4, 8, with n_(EPDCCH)< 104 and using normal cyclic prefix All other cases ePDCCH LocalizedDistributed Localized Distributed format transmission transmissiontransmission transmission 0 2 2 1 1 1 4 4 2 2 2 8 8 4 4 3 16 16 8 8 4 —32 — 16

In distributed transmission, an ePDCCH can be mapped to resourceelements in up to D PRB pairs, where D=2, 4, or 8 (the value of D=16 isalso being considered in 3GPP). In this way, frequency diversity can beachieved for the ePDCCH message. See FIG. 7A for a schematic example inwhich a downlink subframe shows four parts belonging to an ePDCCH whichis mapped to multiple of the enhanced control regions known as PRBpairs, to achieve distributed transmission and frequency diversity orsub-band precoding.

As of September 2012, the 3GPP has not reached agreement as to how fouror eight eREGs respectively should be grouped into the eCCEs. It is alsoan open question as to how the encoded and modulated symbols of anePDCCH message are mapped to the resource elements within the resourcesreserved by its associated eREGs. Further, the number of blind decodesper aggregation level for ePDCCH has not yet been decided in the 3GPPstandardization work. Likewise, how randomization of the search spacefor localized and distributed mappings is generated has not yet beendecided, although it is clear that overlap between ePDCCH candidates ofdifferent aggregation levels will occur also for the ePDCCH, as is thecase for the PDCCH.

Time-Division Duplex (TDD) operation in LTE systems presents additionalchallenges with respect to PDCCH and ePDCCH to PUCCH mapping. Thesechallenges to PUCCH HARQ-ACK resource determination arise from theasymmetry between uplink and downlink. When there are more downlinksubframes than uplink subframes, the one to one mapping used inFrequency-Division Duplex (FDD) mode cannot be reused, since PUCCHresources selected according to this approach will collide with eachother across different downlink subframes. On the other hand, overallHARQ-ACK resource utilization should be considered, since the resourcesfor PUSCH transmission will be reduced if excessive uplink resources arereserved for PUCCH HARQ-ACK transmission. The TDD PUCCH resource forHARQ-ACK transmission in response to legacy PDCCH has been specified inthe technical standardization document 3GPP TS 36.213, “Physical LayerProcedures,” v10.6.0.

FIG. 9 provides an illustration of the allocation of PUCCH resources forPDCCH, in TDD mode. The illustrated example is for four downlinksubframes (SF0, SF1, SF2, and SF3) and one uplink subframe (SF4).Therein the resource determination for HARQ-ACK multiplexing andHARQ-ACK bundling are similar and can be derived as specified in 3GPP TS36.213 v10.6.0, “Physical Layer Procedures”. It can be seen that thePUCCH HARQ-ACK resources will be stacked firstly for the lowest eCCEindex of the DCI that fall within the first one-third CCEs of thecontrol region, across multiple subframes (from SF 0 to SF 3) (markedwith diagonal shading). These PUCCH HARQ-ACK resources are followed bythe DCIs belonging to the second one-third CCEs of the control region(shaded). Finally are the last one-third CCEs (marked withcross-hatching). The design philosophy is that when system load is low,the control region could be automatically reduced by the dynamicsignaling of PCFICH, hence the PUCCH HARQ-ACK resource could becompressed to a continuous region.

TDD PUCCH resource determination for ePDCCH has not been resolved in3GPP RAN1 yet, i.e., no concrete solution is provided. However, aseparate design different from FDD is needed, just as for PDCCH. Due tothe fundamental differences in resource structures, the current designfor PDCCH cannot be reused for ePDCCH. For example, PDCCH is a commoncontrol region (first one to four OFDM symbols) for all UEs while ePDCCHis multiplexed in frequency with PDSCH in a UE-specific manner.Accordingly, techniques for TDD PUCCH HARQ resource allocation for theEnhanced Physical Downlink Control Channel (ePDCCH) in radiocommunication systems are needed.

SUMMARY

According to several embodiments of the techniques disclosed herein,solutions are provided for PUCCH resource determination for HARQ-ACKtransmission in response to ePDCCH-scheduled PDSCH or ePDCCH-indicatedSPS release in a TDD radio communication system. Several differentcategories of embodiments are detailed below, each of which may havedifferent combinations of PUCCH blocking probability, PUCCH resourceutilization efficiency, eNB scheduler complexity and implementationcomplexity.

One example embodiment of the presently disclosed techniques is aprocessing method, suitable for implementation by a wireless device, fordetermining the resources for transmitting hybridautomatic-repeat-request (HARQ) feedback in a wireless communicationnetwork configured for time-division duplexing (TDD) operation. Theexample method begins with receiving downlink control information (DCI)via an Enhanced Physical Downlink Control Channel (ePDCCH) in a downlinksubframe. The received ePDCCH schedules a downlink shared channeltransmission to the wireless device or indicates a release ofsemi-persistent scheduling (SPS) to the wireless device. The methodcontinues with determining a resource index for a Physical UplinkControl Channel (PUCCH) resource based on the lowest enhanced ControlChannel Element (eCCE) index of the received DCI, a device-specificoffset value previously signaled to the wireless device via RadioResource Control (RRC) signaling, and an index i. The index i identifiesthe downlink subframe in a pre-determined set of one or more downlinksubframes associated with an uplink subframe. The determining of thePUCCH resource is performed according to a formula that results in asequential allocation of PUCCH resources in the uplink subframe withrespect to the downlink subframes associated with the uplink subframe,for each of a plurality of sets of ePDCCH resources. The methodcontinues with the transmitting of HARQ feedback in the uplink subframe,using a PUCCH resource that corresponds to the resource index.

In some embodiments, determining the resource index for the PUCCHresource comprises determining the resource index based on the sum of(i) the lowest enhanced eCCE of the received DCI, (ii) thedevice-specific offset value previously signaled to the wireless devicevia RRC signaling, and (iii) the product of the index i and the numberof eCCEs in a set of ePDCCH resources that includes those ePDCCHresources used by the received ePDCCH. In some of these embodiments, theset of ePDCCH resources is set q of a plurality of sets of ePDCCHresources, wherein the uplink subframe is subframe n and the downlinksubframe is subframe n-k_(i), where k_(i) is the i-th element in thepre-determined set of downlink subframes associated with subframe n, thepre-determined set comprising M elements indexed according to k₀, k₁, .. . , k_(M-1), and determining the resource index comprises calculating:n_(PUCCH,i) ⁽¹⁾=i·N_(q) ^(eCCE)+n_(eCCE,i)+N_(UE-PUCCH) ^((q)), wheren_(eCCE,i) is the lowest eCCE index of the received DCI and N_(q)^(eCCE) is the number of eCCEs in ePDCCH set q. The resource index inthese embodiments is derived from n_(PUCCH,i) ⁽¹⁾.

Other embodiments include corresponding operations implemented by anetwork node, e.g., an LTE eNB, in determining the PUCCH resource usedby a wireless device and receiving the HARQ feedback in that resource.Still other embodiments include wireless devices and network nodesconfigured to carry out one or more of the techniques detailed herein.It will be appreciated that other embodiments include variations of andextensions to these enumerated embodiments, in accordance with thedetailed procedures and variants described below.

Of course, the present invention is not limited to the above featuresand advantages. Indeed, those skilled in the art will recognizeadditional features and advantages upon reading the following detaileddescription, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating physical resources as defined in LTE.

FIG. 2 is a diagram of the LTE time-domain structure.

FIG. 3 is a diagram of a PRB pair within an LTE time-frequency grid.

FIG. 4 is a diagram of mapping within an LTE downlink subframe forPDCCH, CRS, etc.

FIG. 5 is a diagram of ePDCCH, as defined in the PDSCH region of adownlink subframe.

FIG. 6 is a diagram of RE/EREG mapping within a PRB pair using normalCP.

FIGS. 7A and 7B illustrate examples of distributed and localized sets ofPRBs, respectively, as used for ePDCCH.

FIG. 8 illustrates a difference between a control channel element (CCE)and an enhanced CCE (eCCE) with respect to mapping around cell-specificreference symbols (CRS).

FIG. 9 illustrates the allocation of PUCCH resources for PDCCH, in TDDmode.

FIG. 10 is a block diagram of an example embodiment of a network nodeand a wireless device that are configured according to the teachingsherein.

FIG. 11 is a block diagram of example details for the network node andwireless device of FIG. 10.

FIG. 12 depicts an exemplary ePDCCH resource configuration examplehaving three ePDCCH sets with 4 PRBs per set.

FIG. 13 illustrates an example of a PUCCH HARQ-ACK resource structureaccording to an embodiment.

FIG. 14 illustrates an example of a PUCCH HARQ-ACK resource structureaccording to another embodiment.

FIG. 15 illustrates an example of a PUCCH HARQ-ACK resource structureaccording to another embodiment.

FIG. 16 illustrates an example of a PUCCH HARQ-ACK resource structureaccording to another embodiment.

FIG. 17 illustrates an example of a PUCCH HARQ-ACK resource structureaccording to another embodiment.

FIG. 18 is a logic flow diagram of one embodiment of a method ofprocessing at a wireless device.

FIG. 19 is a logic flow diagram of one embodiment of a method ofprocessing at a network node.

DETAILED DESCRIPTION

FIG. 10 illustrates a network node 10 and a wireless device 12. Wirelessdevice 12 is configured to carry out terminal-side (i.e., UE-side)processing for the PUCCH allocation and hybrid automatic-repeat request(HARQ)-related teachings herein. In particular, the wireless device 12is configured to determine, using one or more of several techniquesdetailed below, a particular Physical Uplink Control Channel (PUCCH) forhybrid automatic-repeat-request (HARQ) feedback in response to anePDCCH-scheduled PDSCH transmission or an ePDCCH-indicated SPS release,in TDD systems. Correspondingly, the network node 10 is configured tocarry out complementary network-side processing for determining thePUCCH resource used by a wireless device 12 for HARQ feedback.

The network node 10 includes one or more processing circuits 14 andassociated memory/storage 16. The memory/storage 16 may be one or moretypes of computer-readable medium, such as a mix of volatile, workingmemory and non-volatile configuration and program memory or storage. Thenetwork node 10 further includes one or more communication interfaces18. The communication interface(s) 18 depend on the nature of thenetwork node 10. In a base station or other radio node example, thecommunication interface(s) 18 include a radio transceiver—e.g., pools ofradio transmission, reception, and processing circuitry—forcommunicating with any number of wireless devices 12 in any one or morecells of a wireless communication network. Further, the network node 10may support Carrier Aggregation (CA) operation, Time Division Duplex(TDD) operation, Multiple-Input-Multiple-Output (MIMO) operation, etc.Additionally, the communication interface(s) 18 may includeinter-base-station interfaces and/or backhaul or other CN communicationinterfaces. In an LTE-based example where the network node 10 comprisesan eNodeB, the communication interface(s) 18 include an “X2” interfacefor inter-eNodeB communications.

Correspondingly, the wireless device 12 may be a cellularradiotelephone—smartphone, feature phone, tablet, etc.—or may be anetwork adaptor, card, modem or other such interface device, or may be alaptop computer or other such device with integrated wirelesscommunication capabilities. Of course, these examples are non-limitingand the wireless device 12 should be broadly understood as acommunications transceiver configured for network operation according tothe teachings herein. Further, it should be appreciated that referencesherein to “user equipment” or “UE” should be understood to refer moregenerally to a wireless device as pictured in FIG. 10.

The wireless device 12 includes a transceiver circuit 20, which includesa receiver 22 and a transmitter 24, which are cellular radio circuits,for example. The illustrated wireless device 12 further includes one ormore processing circuits 26, which include or are associated with one ormore memory/storage devices or circuits 28. The memory/storage 28includes, for example, one or more types of computer-readable medium.Example media include a mix of volatile, working memory and non-volatileconfiguration and program memory or other storage—e.g., Random AccessMemory (RAM), Read-Only Memory (ROM), Electrically-EraseableProgrammable Read-Only Memory (EEPROM), Flash memory, and the like.

Those of ordinary skill in the art will appreciate that the transmitter24 and/or receiver 22 each may comprise a mix of analog and digitalcircuits. For example, the receiver 22 in one or more embodimentscomprises a receiver front-end circuit, which is not explicitly shown inFIG. 10. Such circuitry generates one or more streams of digital signalsamples corresponding to antenna-received signal(s) and receiverprocessing circuits—e.g., baseband digital processing circuitry andassociated buffer memory—operate on the digital samples. Exampleoperations include linearization or other channel compensation, possiblywith interference suppression, and symbol demodulation and decoding, forrecovering transmitted information.

Those of ordinary skill in the art will appreciate that FIG. 10illustrates high-level physical circuit arrangements and that thenetwork node 10 and the wireless device 12 generally will includedigital processing circuits and associated memory or othercomputer-readable medium, for storing configuration data, operational orworking data, and for storing computer program instructions. In at leastsome of the embodiments contemplated herein, the network-side anddevice-side functionality is realized at least in part through theprogrammatic configuration of digital processing circuitry, based on theexecution by that circuitry of stored computer program instructions. Thefunctional circuits realized in this manner shall be understood as“machines” specially adapted for the purpose(s) described herein. Theprocessing circuit 14 in the network node 10 and the processing circuit26 in the wireless device 12 may be at least partly configured in thismanner.

FIG. 11 provides example details for both the network node 10 and thewireless device 12 where the network node 10 is an eNodeB configured foroperation in an LTE network, or is another type of base station or radionode. Consequently, the network node 10 in such embodiments includes RFinterface circuitry 30, which represents or is included in thecommunication interface(s) 18 introduced in FIG. 10. Further, theprocessing circuit 14, which may comprise one or more microprocessors,DSPs, or other digital processing circuitry, includes a control circuit32 that is configured according to the teachings herein. The controlcircuit 32 also may be referred to as a processing circuit, a processingunit, or a control unit. In at least one embodiment, the control circuit32 is specially adapted according to the network-side teachings herein,based on its execution of stored computer program instructions from acomputer program 34 stored in the memory/storage 16.

The network node 10 may comprise a rack or cabinet of processingcircuits using a card/backplane arrangement and may include a host ofadditional processing circuits/functions not shown in the simplifieddiagram. More generally, the processing circuit 14 may comprise any oneor more computer-based circuits that control at leastcommunication-related processing—e.g., transmit and receive operationsthrough the RF interface circuitry 30. Thus, the processing circuit 14may include a number of other functional circuits not shown, such asuser-scheduling circuits to control uplink and/or downlink transmissionsamong a plurality of wireless devices 12 being supported by the networknode 10, and may include one or more conditions-determination circuits,such as for determining network loading, e.g., for one or more servedcells and/or one or more neighboring cells.

In a similar fashion, the wireless device 12 may be configured tooperate according to any one or more wireless communication standards,such as the WCDMA and/or LTE and LTE-A standards. Broadly, the wirelessdevice 12 may support more than one Radio Access Technology (RAT), suchas may be used in heterogeneous network deployments involving macrocells and base stations and micro cells and base stations, where macroand micro base stations may or may not use the same RAT(s). Thetransceiver circuitry 20 therefore may comprise one or more cellularradios, and is shown overlapping the processing circuit 26 to indicatethat the receiver 22 and/or transmitter 24 may be implemented in a mixof analog and digital circuits, including baseband processing circuitscomprising or otherwise included in the processing circuit 26. In onesuch example, the processing circuit 26 implements one or more receivedsignal processing chains that provide, for example, received signallinearization and/or interference compensation, symbol detection andcorresponding decoding (Viterbi, joint detection, etc.), for therecovery of transmitted information.

A control circuit 36 is implemented within or as part of the processingcircuit 26 of the wireless device and the memory/storage 28 in someembodiments stores one or more computer programs 38 and/or configurationdata. The control circuit 36 carries out device-side processingregarding PRB set expansion, as taught herein. In at least oneembodiment, the control circuit 36 is implemented based on the executionof computer program instructions by the processing circuit 26, where theprogram instructions are stored as a computer program 38 in thestorage/memory 28, for example.

It will be appreciated that references throughout the present disclosureto “one embodiment” or “an embodiment” mean that a particular feature,structure, or characteristic described in connection with an embodimentis included in at least one embodiment or aspect of the presentlydisclosed inventive techniques. Thus, the appearance of the phrases “inone embodiment” or “in an embodiment” in various places throughout thespecification do not necessarily all refer to the same embodiment.Further, the particular features, structures or characteristics may becombined in any suitable manner in one or more embodiments.

According to several embodiments of the presently disclosed techniques,solutions are provided for PUCCH resource determination for HARQ-ACKtransmission in response to ePDCCH-scheduled PDSCH or ePDCCH-indicatedSPS release in a TDD radio communication system. Several differentcategories of embodiments are described below, which have differentcombinations of PUCCH blocking probability, PUCCH resource utilizationefficiency, eNB scheduler complexity and implementation complexity. Forconvenience, these embodiments are described under headings of“Embodiment 1,” “Embodiment 2,” etc. However it should be appreciated bythose skilled in the art that each of these categories may includeseveral variations, that these embodiments are not necessarily mutuallyexclusive, and that various aspects of these embodiments can be usedtogether.

The embodiments described below can fit into (be used in conjunctionwith) different FDD PUCCH HARQ-ACK resource allocation schemes forePDCCH. To provide context for the described embodiments, the proposalfor FDD PUCCH HARQ-ACK resource allocation described in a 3GPPsubmission numbered R1-123870 and entitled “PUCCH resource allocationfor ePDCCH” for distributed ePDCCH is described below. (R1-123870 isavailable at http://www.3gpp.org/ftp/tsg_ran/wg1_rl1/TSGR1_70/Docs/.)However those skilled in the art will appreciate that the presentlydisclosed embodiments are not limited to usage with this FDD resourceallocation scheme and that, in fact, these TDD resource allocationschemes can be used with other FDD resource allocation schemes.

However, for context, the PUCCH resource in FDD mode is determined byn_(PUCCH) ⁽¹⁾=n_(eCCE)+N_(UE-PUCCH) ^((q)), where n_(eCCE) is the lowesteCCE index of the DCI detected on ePDCCH and N_(UE-PUCCH) ^((q)) is aUE-specific offset, signaled to the UE by Radio Resource Control (RRC)signaling. It has been agreed by 3GPP that a UE can be configured with Qsets of N PRB pairs respectively, to be used for ePDCCH. Each set canhave one of several different sizes, e.g., 2, 4, 8 PRB pairs. In thefollowing, it is assumed for purposes of illustration that the UE isconfigured with three ePDCCH sets, and with four PRBs per set as shownin FIG. 12. Each set of PRBs is configured with a PUCCH HARQ-ACKresource starting position N_(UE-PUCCH) ^((q)), q=1, . . . , Q, and thePRB pairs of each set are distributed across the frequency band, asshown in FIG. 12, where diagonally-marked, shaded, and cross-hatchedblocks are used to represent elements of sets 1, 2 and 3, respectively.As mentioned above, the proposed solutions described in detail belowcould be easily extended to any ePDCCH resource configurations and theexample of FIG. 12 (which is used as a baseline reference to describethe embodiments below) can be varied, e.g., to include more or fewerePDCCH sets and/or more or fewer PRBs per set.

Embodiment 1

According to this embodiment and variants thereof, for PDSCHtransmission indicated by the detection of corresponding ePDCCH or anePDCCH indicating downlink SPS release within subframe n−k_(i), wherek_(i) belongs to a set of M elements k_(i)∈{k₁, k₂, . . . k_(M-1)} asdefined in Table 10.1.3.1-1 of 3GPP TS 36.213, v10.6.0, the UE shalldetermine the PUCCH resource n_(PUCCH,i) ⁽¹⁾ so that the allocated PUCCHresources for a given subframe k follows the following rule:

n _(PUCCH,i) ⁽¹⁾ =i·N _(q) ^(eCCE) +n _(eCCE,i) +N _(UE-PUCCH)^((q))  (2)

where n_(eCCE,i), which is the lowest eCCE index of the DCI detected onePDCCH, belongs to ePDCCH set q of subframe n−k_(i), 0≤i≤M−1. M is thenumber of elements in the set defined in Table 10.1.3.1-1, and N_(q)^(eCCE) is the number of eCCEs in ePDCCH set q. Note that although thisand the following embodiments refer to the UE determining the relevantPUCCH HARQ resources, it will be understood by those skilled in the artthat both the UE and its serving base station (e.g., eNB, or anothernetwork node connected thereto) will need to determine the relevantPUCCH HARQ resources for the connection between the UE and its servingbase station so that, e.g., both nodes know which resource the UE/BS isusing to be able to decode the ACK/NAK correctly. Accordingly, althoughother embodiments described below may not explicitly restate this, itshall be understood that each embodiment can be implemented in both theUE and the network side, e.g., base station.

Following equation (2) above, the PUCCH HARQ-ACK resource will bestacked across subframes for each ePDCCH set independently, as shown inFIG. 13. Thus, for each ePDDCH set, the PUCCH ACK/NAK resource isstacked across the subframes sequentially, i.e., DCI messages belongingto subframe 0 first, followed by DCIs belonging to subframe 1 . . . etc.Therein, each of the columns are associated with a different ePDCCH set(yellow(Y), blue(B) and red(R)) as indicated. An advantage of thisalternative is simplicity and the resource utilization will be effectiveat low system load if the scheduler could always allocate DCI to theePDCCH Set 1 with high priority. However, this solution increases thePUCCH HARQ-ACK blocking probability since it introduces additional PUCCHresource blocking among different subframes. This also makes the eNBscheduler more complicated.

Note that equation (2) assumes that there are an equal number of eCCEsper each subframe in the first i subframes of the M downlink subframesthat are associated with uplink subframe n. This may not always be thecase, in which case equation (2) may not always apply. However, thesequential stacking of PUCCH HARQ-ACK resources, where resources foreach of the Q ePDCCH set are stacked independently, as shown in FIG. 13,may still be applied in cases where there is an unequal number of eCCEsacross the subframes. The same advantages described above apply.

In an extension to the formula in equation (2), the PUCCH resources arecompressed between the different sets q together with a varying M forthe HARQ-ACK feedback in the uplink. In an embodiment, an HARQ-ACKcompression scheme is introduced that compresses the HARQ-ACK PUCCHresources based on M. In a further example the compression scheme worksby compressing the HARQ-ACK PUCCH resources between different sets qtogether. An example of such a compression scheme is shown here by usingeq. (2) as a base, resulting in equation (2a) below. However it is alsopossible to extend the other embodiments described below in a similarmanner.

$\begin{matrix}{n_{{PUCCH},i}^{(1)} = {{i \cdot N_{q}^{eCCE}} + n_{{eCCE},i} + N_{{UE}\text{-}{PUCCH}}^{(q)} - {\sum\limits_{q^{\prime} = 0}^{q - 1}{\left( {M_{\max} - M} \right) \cdot N_{q^{\prime}}^{eCCE}}}}} & \left( {2a} \right)\end{matrix}$

where the definitions for equation 2a are the same as in equation 2,with the addition that N⁻¹ ^(eCCE)=0 and M_(max) is the maximum M overall possible HARQ-ACK feedback subframes for a given UL/DLconfiguration, as set forth according to table 10.1.3.1-1 in 3GPP TS36.213. v10.6.0. For example, M_(max) can be 3 in the event that UL/DLconfiguration 3 is used.

Embodiment 2

According to this embodiment and variants thereof, for PDSCHtransmission indicated by the detection of corresponding ePDCCH or anePDCCH indicating downlink SPS release within subframe n−k_(i), wherek_(i) belongs to a set of M elements k_(i)∈{k₁, k₂, . . . k_(M-1)} asdefined in Table 10.1.3.1-1 in 3GPP TS 36.213, v10.6.0, the UE shalldetermine the PUCCH resource n_(PUCCH,i,k) ⁽¹⁾ according to thisembodiment as follows:

$\begin{matrix}{n_{{PUCCH},i,q}^{(1)} = {n_{{eCCE},i} + N_{{UE}\text{-}{PUCCH}}^{(0)} + {i \cdot N_{eCCE}^{(q)}} + {\sum\limits_{q^{\prime} = {- 1}}^{q - 1}{M \cdot N_{eCCE}^{(q^{\prime})}}}}} & (3)\end{matrix}$

where n_(ECCE,i,k) belongs to ePDCCH set q of subframe n−k_(i), 0≤i≤M−1;M is the number of elements in the set defined in Table 10.1.3.1-1 in3GPP TS 36.213, v10.6.0; N_(UE-PUCCH) ⁽⁰⁾ is a UE-specific offsetparameter for the set with the lowest PUCCH resource starting positionand N_(eCCE) ^((q′)) is the total amount of CCE in an set q′ persubframe with N_(eCCE) ⁽⁻¹⁾=0. Following equation (3) above, the PUCCHHARQ-ACK resource will be stacked across subframes after each other perset q as shown in FIG. 14. Thus, the PUCCH ACK/NAK resources accordingto this embodiment are stacked for each ePDCCH set, one by one. Startingfrom the set with the lowest PUCCH ACK/NAK starting position, the PUCCHACK/NAK resources are stacked across the subframes sequentially, i.e.,DCI messages belonging to subframe 0 first followed by DCIs belonging tosubframe 1, etc. The set with second lowest PUCCH ACK/NAK startingposition will be stacked beginning at the end of region for the firstset, then the set with the third lowest PUCCH ACK/NAK starting position,etc. In FIG. 14, each of the different ePDCCH sets is indicated bydiagonally-marked, shaded, and cross-hatched blocks. An advantage withthis embodiment is that a single parameter N_(UE-PUCCH) ⁽⁰⁾ is able toprovide unique PUCCH resources for all of the different sets at the sametime. Thus, there will be no resource collisions among different sets,as well as no resource collisions between subframes.

Embodiment 3

In this third embodiment and variants thereof, the PUCCH resources fromthe corresponding ePDCCH are stacked first within one subframe for allsets. This is quite distinct from embodiment 2, where the PUCCHresources are stacked per all subframes within a set. Thus, for PDSCHtransmission indicated by the detection of corresponding ePDCCH or anePDCCH indicating downlink SPS release within subframe n−k_(i), wherek_(i) belongs to a set of M elements k_(i)∈{k₁, k₂, . . . k_(M-1)} asdefined in Table 10.1.3.1-1 in 3GPP TS 36.213, v10.6.0, the UE shalldetermine the PUCCH resource n_(PUCCH,i) ⁽¹⁾ for this third embodimentas follows:

n _(PUCCH,i) ⁽¹⁾ =i·N _(PUCCH) ^(ePDCCH) +n _(eCCE,i) +N _(UE-PUCCH)^((k))  (4)

where n_(eCCE,i) belongs to ePDCCH set q of subframe n−k_(i), 0≤i≤M−1; Mis the number of elements in the set defined in Table 10.1.3.1-1 of 3GPPTS 36.213, v. 10.6.0; and N_(PUCCH) ^(ePDCCH) is the total number ofPUCCH resources in all sets within one subframe. Following equation (4)above, the PUCCH HARQ-ACK resource in different subframes will not beoverlapped as shown in the example of FIG. 15, again withdiagonally-marked blocks indicating subframes belonging to a first set,shaded blocks indicating subframes belonging to a second set andcross-hatched blocks indicating subframes belonging to a third set.Thus, according to this embodiment, the PUCCH ACK/NAK resources arestacked for each subframe sequentially. Starting from subframe 0, thePUCCH ACK/NAK resources are stacked separately for each set. Note thatthe size of the resource region within one subframe depends on the sizeof each ePDCCH set and the PUCCH starting position of each set. ThePUCCH ACK/NAK resource for subframe 1 starts from the end of resourceregion for subframe 0 in the same manner, then subframe 2 is aftersubframe 1, etc. N_(PUCCH) ^(ePDCCH) can for example, either becalculated by the UE based on all configured sets or signaled from theeNodeB. This solution also has low complexity. Compared to the firstembodiment, there will be no resource collisions among differentsubframes but the resource utilization is relatively low, since theresources are reserved even when there is no user scheduled within aparticular subframe.

Embodiment 4

According to this fourth embodiment and variants thereof, for PDSCHtransmission indicated by the detection of corresponding ePDCCH or anePDCCH indicating downlink SPS release within subframe n−k_(i), wherek_(i) belongs to a set of M elements k_(i)∈{c k₁, k₂, . . . k_(M-1)} asdefined in Table 10.1.3.1-1 in 3GPP TS 36.213, v10.6.0, the UE shalldetermine the PUCCH resource n_(PUCCH,i) ⁽¹⁾ according to thisembodiment as follows:

n _(PUCCH,i) ⁽¹⁾ =n _(eCCE,i) +N _(UE-PUCCH) ^((i,q))  (5)

where n_(eCCE,i) belongs to ePDCCH set k of subframe n−k_(i), 0≤i≤M−1. Mis the number of elements in the set defined in Table 10.1.3.1-1, andN_(UE-PUCCH) ^((i,q)) is the UE-specific PUCCH resource start positionfor ePDCCH set q for index i. This solution provides full flexibility toconfigure PUCCH HARQ-ACK regions for each subframe. On one hand, thisgives the eNB full freedom to manage PUCCH HARQ-ACK resources. Thisembodiment can provide orthogonal resources for all sets in a cell, evenif some UEs are only configured with a subset of them. The drawback ofthis embodiment is the additional signaling needed.

One example of the PUCCH resource configuration according to thisembodiment is illustrated in FIG. 16, again with diagonally-markedblocks indicating subframes belonging to a first set, shaded blocksindicating subframes belonging to a second set and cross-hatched blocksindicating subframes belonging to a third set. From FIG. 16 it can beseen that, according to this embodiment, the PUCCH ACK/NAK resources foreach subframe and each set are stacked completely independently fromeach other.

As a variant of this fourth embodiment, for PDSCH transmission indicatedby the detection of corresponding ePDCCH or an ePDCCH indicatingdownlink SPS release within subframe n−k_(i), where k_(i) belongs to aset of M elements k_(i) ∈{k₁, k₂, . . . k_(M-1)} as defined in Table10.1.3.1-1 in 3GPP TS 36.213, v10.6.0, the UE shall determine the PUCCHresource n_(PUCCH,i) ⁽¹⁾ according to this embodiment as follows:

n _(PUCCH,i) ⁽¹⁾ =n _(eCCE,i) +i·N _(UE-PUCCH-OFFSET) ^((q)) +N_(UE-PUCCH) ^((q))  (6)

where n_(eCCE,i) belongs to ePDCCH set k of subframe n−k_(i), 0≤i≤M−1; Mis the number of elements in the set defined in Table 10.1.3.1-1;N_(UE-PUCCH) ^((q)) is the UE-specific PUCCH resource start position forePDCCH set q; and N_(UE-PUCCH-OFFSET) ^((q)) is the UE-specific offsetvalue for set q. This embodiment has less flexibility than embodiment 3,but with lower signaling overhead. This embodiment can provideorthogonal resources for all sets in a cell even if some UEs are onlyconfigured with a subset of them. If N_(UE-PUCCH-OFFSET) ^((q)) is thesame for all sets, then this becomes the same as embodiment 2, with aconfigured N_(PUCCH) ^(ePDCCH).

Fifth Embodiment

According to this fifth embodiment and variants thereof, for PDSCHtransmission indicated by the detection of corresponding ePDCCH or anePDCCH indicating downlink SPS release within subframe n−k_(i), wherek_(i) belongs to a set of M elements k_(i) ∈{k₁, k₂, . . . k_(M-1)} asdefined in Table 10.1.3.1-1 in 3GPP TS 36.213, v10.6.0, the UE shalldetermine the PUCCH resource n_(PUCCH,i) ⁽¹⁾ as follows:

$\begin{matrix}{n_{{PUCCH},i}^{(1)} = {{\left( {M - m - 1} \right) \cdot {\sum\limits_{{j = 0},{j \in V_{C}}}^{c}\left( {{N_{C}^{eCCE}(j)} - {N_{C}^{eCCE}\left( {j - 1} \right)}} \right)}} + {m \cdot {\sum\limits_{{j = 0},{j \in V_{C}}}^{c}\left( {{N_{C}^{eCCE}\left( {j + 1} \right)} - {N_{C}^{eCCE}(j)}} \right)}} + n_{{eCCE},i} + N_{{UE}\text{-}{PUCCH}}^{(q)}}} & (7)\end{matrix}$

where n_(eCCE,i) belongs to ePDCCH set q of subframe n−k_(i), 0≤i≤M−1;and M is the number of elements in the set defined in Table 10.1.3.1-1.In this embodiment, the UE first selects a c out of {0, 1, 2, . . . ,2Q}, where the selected c makes N_(C)^(eCCE)(c)≤(n_(eCCE,i)+N_(UE-PUCCH) ^((k)))<N_(C) ^(eCCE)(c+1), whereN_(C) ^(eCCE)=sort(N_(UE-PUCCH) ⁽⁰⁾, N_(UE-PUCCH) ⁽⁰⁾+N₀ ^(eCCE), . . ., N_(UE-PUCCH) ^((Q)), N_(UE-PUCCH) ^((Q))+N_(Q) ^(eCCE)), the functionsort(⋅) is with increasing order, N_(C) ^(eCCE)(−1)=N_(C) ^(eCCE)(0),V_(c) is a set of c which satisfies the following condition

$V_{c} = {\left\{ {c{\left\lbrack {{N_{C}^{eCCE}(c)},{N_{C}^{eCCe}\left( {c + 1} \right)}} \right\rbrack \in {\bigcup\limits_{k}\left( \left\lbrack {N_{{UE}\text{-}{PUCCH}}^{(q)},{N_{{UE}\text{-}{PUCCH}}^{(q)} + N_{q}^{eCCE}}} \right\rbrack \right)}}} \right\}.}$

This solution has relatively high complexity but has the advantage ofhigh resource utilization efficiency. One example of the PUCCH resourceconfiguration according to this embodiment is illustrated in FIG. 17.Thus, according to this embodiment, based on the PUCCH ACK/NAK resourcesstarting position and the size of resource region for each ePDCCH set,the whole PUCCH ACK/NAK region is first divided into multiplenon-overlapping subregions in an increasing order. For example, startingfrom the first subregion, the PUCCH ACK/NAK resources are stacked acrosssubframes, i.e., DCI messages belonging to (subframe 0, subregion 0)followed by DCIs belonging to (subframe 1, subregion 0), then DCsIbelonging to (subframe 2, subregion 0), etc. Then for the secondsubregion, the PUCCH ACK/NAK resources are stacked in the same mannerfrom the end of first subregion. The same principles are then appliedfor the rest of the subregions.

Embodiments 6-10

As an additional variation of any of the previously describedembodiments 1-5, an additional correction term can be added to theresource calculation. This term relates to the size of the legacy PDCCHregion. Such alternative embodiments result in the PUCCH resource thatis used being scaled by the size of the PDCCH region in all thesubframes that are part of the HARQ-ACK window. It is further possibleto foresee that the number of PDCCH resources may be approximatelyderived and not be exactly the number that is derived.

This modification is exemplified in equation (8) below, using embodiment1, but the same modification can be applied to any embodiment describedherein. With this extension the UE shall determine the PUCCH resourcen_(PUCCH,i) ⁽¹⁾ as follows:

n _(PUCCH,i) ⁽¹⁾ =i·N _(q) ^(eCCE) +n _(eCCE,i) +N _(UE-PUCCH)^((q))+(M−1)*N ^(CCE),  (8)

where N^(CCE) is the maximum number of CCEs available on the legacyPDCCH in a subframe. In a more general formulation the UE shalldetermine the PUCCH resource n_(PUCCH,i) ⁽¹⁾ as follows:

$\begin{matrix}{{n_{{PUCCH},i}^{(1)} = {{i \cdot N_{k}^{eCCE}} + n_{{eCCE},i} + N_{{UE}\text{-}{PUCCH}}^{(k)} + {\sum\limits_{j = 1}^{M - 1}N_{j}^{CCE}}}},} & (9)\end{matrix}$

where N_(j) ^(CCE) is the largest number of available CCEs on the legacyPDCCH in subframe n−k_(j). In other embodiments the sum may instead gofrom j=0.

Among other things, the foregoing embodiments provide several solutionsfor PUCCH resource determination for HARQ-ACK transmission in responseto ePDCCH-scheduled PDSCH or ePDCCH-indicated SPS release in a TDDsystem. These embodiments offer different alternatives with tradeoffsamong, for example, PUCCH blocking probability, PUCCH resourceutilization efficiency, eNB scheduler complexity and implementationcomplexity.

From the foregoing discussion of various exemplary embodiments, it willbe appreciated that these and other embodiments will, when implemented,have impacts on various nodes in a radio communication system. Forexample, the various PUCCH resource determination schemes for HARQ-ACKtransmission in response to ePDCCH-scheduled PDSCH or ePDCCH-indicatedSPS release in a TDD system described above may need to be implementedat both a network side node (e.g., eNB) and at the user equipment.

FIG. 18 illustrates a non-limiting example embodiment of a processingmethod 1800, which corresponds to the above-described processing for thewireless device 12, for at least embodiment 1. The method 1800 isdirected to a technique for determining the resources for transmittinghybrid automatic-repeat-request (HARD) feedback in a wirelesscommunication network configured for time-division duplexing (TDD)operation. The method begins, as shown at block 1810, with receivingdownlink control information (DCI) via an Enhanced Physical DownlinkControl Channel (ePDCCH) in a downlink subframe. The received ePDCCHschedules a downlink shared channel transmission to the wireless deviceor indicates a release of semi-persistent scheduling (SPS) to thewireless device.

As shown at block 1820, the method continues with determining a resourceindex for a Physical Uplink Control Channel (PUCCH) resource based onthe lowest enhanced Control Channel Element (eCCE) index of the receivedDCI, a device-specific offset value previously signaled to the wirelessdevice via Radio Resource Control (RRC) signaling, and an index i. Theindex i identifies the downlink subframe in a pre-determined set of oneor more downlink subframes associated with an uplink subframe. Thedetermining of the PUCCH resource is performed according to a formulathat results in a sequential allocation of PUCCH resources in the uplinksubframe with respect to the downlink subframes associated with theuplink subframe, for each of a plurality of sets of ePDCCH resources. Asshown at block 1830, the method continues with the transmitting of HARQfeedback in the uplink subframe, using a PUCCH resource that correspondsto the resource index.

In some embodiments, such as those described above under the heading“Embodiment 1,” determining the resource index for the PUCCH resourcecomprises determining the resource index based on the sum of (i) thelowest enhanced eCCE of the received DCI, (ii) the device-specificoffset value previously signaled to the wireless device via RRCsignaling, and (iii) the product of the index i and the number of eCCEsin a set of ePDCCH resources that includes those ePDCCH resources usedby the received ePDCCH. In some of these embodiments, determining theresource index comprises calculating the resource index according toequation (2), as set forth above.

As noted earlier, the operations carried out by a wireless device 12 indetermining the PUCCH resource and transmitting HARQ feedback in thatresource are complemented by corresponding operations in a network node10, e.g., an LTE eNB, in determining the PUCCH resource used by thewireless device 12 and receiving the HARQ feedback in that resource.FIG. 19 thus illustrates a non-limiting example embodiment of aprocessing method 1900, which corresponds to this processing for anetwork node 10, for at least embodiment 1. Method 1900 is thusgenerally directed to a technique for determining the resources forreceiving hybrid automatic-repeat-request (HARQ) feedback in a wirelesscommunication network configured for time-division duplexing (TDD)operation. The method begins, as shown at block 1910, with transmittingdownlink control information (DCI) to a wireless device, via an EnhancedPhysical Downlink Control Channel (ePDCCH) in a downlink subframe. Thetransmitted ePDCCH schedules a downlink shared channel transmission tothe wireless device or indicates a release of semi-persistent scheduling(SPS) to the wireless device.

As shown at block 1920, the method continues with determining a resourceindex for a Physical Uplink Control Channel (PUCCH) resource based onthe lowest enhanced Control Channel Element (eCCE) index of thetransmitted DCI, a device-specific offset value previously signaled tothe wireless device via Radio Resource Control (RRC) signaling, and anindex i. The index i identifies the downlink subframe in apre-determined set of one or more downlink subframes associated with anuplink subframe. The determining of the PUCCH resource is performedaccording to a formula that results in a sequential allocation of PUCCHresources in the uplink subframe with respect to the downlink subframesassociated with the uplink subframe, for each of a plurality of sets ofePDCCH resources. As shown at block 1910, the method continues with thereceiving of HARQ feedback in the uplink subframe, using a PUCCHresource that corresponds to the resource index.

In some embodiments, such as those described above under the heading“Embodiment 1,” determining the resource index for the PUCCH resourcecomprises determining the resource index based on the sum of (i) thelowest enhanced eCCE of the transmitted DCI, (ii) the device-specificoffset value previously signaled to the wireless device via RRCsignaling, and (iii) the product of the index i and the number of eCCEsin a set of ePDCCH resources that includes those ePDCCH resources usedby the transmitted ePDCCH. In some of these embodiments, determining theresource index comprises calculating the resource index according toequation (2), as set forth above.

With the above examples in mind, it should be clear that the teachingsherein provide several solutions for PUCCH resource determination forHARQ-ACK transmission in response to ePDCCH-scheduled PDSCH orePDCCH-indicated SPS release in a TDD system. The different alternativesprovide different tradeoffs among PUCCH blocking probability, PUCCHresource utilization efficiency, eNB scheduler complexity andimplementation complexity.

It will be appreciated by the person of skill in the art that variousmodifications may be made to the above described embodiments withoutdeparting from the scope of the present invention. The specificembodiments described above should therefore be considered exemplaryrather than limiting the scope of the invention. Because it is notpossible, of course, to describe every conceivable combination ofcomponents or techniques, those skilled in the art will appreciate thatthe present invention can be implemented in other ways than thosespecifically set forth herein, without departing from essentialcharacteristics of the invention. The present embodiments are thus to beconsidered in all respects as illustrative and not restrictive.

It will be understood that although the terms first, second, third, etc.may be used herein to describe various elements/operations, theseelements/operations should not be limited by these terms. These termsare only used to distinguish one element/operation from anotherelement/operation. Thus a first element/operation in some embodimentscould be termed a second element/operation in other embodiments withoutdeparting from the teachings of present inventive concepts. The samereference numerals or the same reference designators denote the same orsimilar elements throughout the specification.

As used herein, the terms “comprise”, “comprising”, “comprises”,“include”, “including”, “includes”, “have”, “has”, “having”, or variantsthereof are open-ended, and include one or more stated features,integers, elements, steps, components or functions but does not precludethe presence or addition of one or more other features, integers,elements, steps, components, functions or groups thereof.

Example embodiments are described herein with reference to blockdiagrams and/or flowchart illustrations of computer-implemented methods,apparatus (systems and/or devices) and/or computer program products. Itis understood that a block of the block diagrams and/or flowchartillustrations, and combinations of blocks in the block diagrams and/orflowchart illustrations, can be implemented by computer programinstructions that are performed by one or more computer circuits. Thesecomputer program instructions may be provided to a processor circuit ofa general purpose computer circuit, special purpose computer circuit,and/or other programmable data processing circuit to produce a machine,such that the instructions, which execute via the processor of thecomputer and/or other programmable data processing apparatus, transformand control transistors, values stored in memory locations, and otherhardware components within such circuitry to implement thefunctions/acts specified in the block diagrams and/or flowchart block orblocks, and thereby create means (functionality) and/or structure forimplementing the functions/acts specified in the block diagrams and/orflowchart block(s).

These computer program instructions may also be stored in a tangiblecomputer-readable medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instructions whichimplement the functions/acts specified in the block diagrams and/orflowchart block or blocks. Accordingly, embodiments of present inventiveconcepts may be embodied in hardware and/or in software (includingfirmware, resident software, micro-code, etc.) running on a processorsuch as a digital signal processor, which may collectively be referredto as “circuitry,” “a module” or variants thereof.

It should also be noted that in some alternate implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved. Moreover, the functionality of a given block of the flowchartsand/or block diagrams may be separated into multiple blocks and/or thefunctionality of two or more blocks of the flowcharts and/or blockdiagrams may be at least partially integrated. Finally, other blocks maybe added/inserted between the blocks that are illustrated, and/orblocks/operations may be omitted without departing from the scope ofinventive concepts. Moreover, although some of the diagrams includearrows on communication paths to show a primary direction ofcommunication, it is to be understood that communication may occur inthe opposite direction to the depicted arrows.

Many variations and modifications can be made to the embodiments withoutsubstantially departing from the principles of the present inventiveconcepts. All such variations and modifications are intended to beincluded herein within the scope of present inventive concepts. Thus, tothe maximum extent allowed by law, the scope of present inventiveconcepts are to be determined by the broadest permissible interpretationof the present disclosure, and shall not be restricted or limited by theforegoing detailed description.

What is claimed is:
 1. A method in a wireless device operating in awireless communication network configured for time-division duplexing(TDD) operation, said method comprising: receiving downlink controlinformation (DCI) via a control channel in a downlink subframe, thereceived downlink control channel scheduling a downlink shared channeltransmission to the wireless device; determining a resource index for anuplink control channel resource based on a device-specific offset valuepreviously signaled to the wireless device and an index i, wherein theindex i identifies the downlink subframe in a pre-determined set of oneor more downlink subframes associated with an uplink subframe, whereinsaid determining is according to a formula that results in a sequentialallocation of uplink control channel resources in the uplink subframewith respect to the downlink subframes associated with the uplinksubframe, for each of a plurality of sets of downlink control channelresources; and transmitting hybrid automatic-repeat-request (HARQ)feedback in the uplink subframe, using an uplink control channelresource corresponding to the resource index.
 2. The method of claim 1,wherein determining the resource index for the uplink control channelresource comprises determining the resource index based on the sum of(i) the lowest control channel element of the received DCI, (ii) thedevice-specific offset value previously signaled to the wireless device,and (iii) the product of the index i and the number of control channelelements in a set of downlink control channel resources that includesthose downlink control channel resources used by the received downlinkcontrol channel.
 3. The method of claim 2, wherein the set of downlinkcontrol channel resources is set q of a plurality of sets of downlinkcontrol channel resources, wherein the uplink subframe is subframe n andthe downlink subframe is subframe n-k_(i), where k_(i) is the i-thelement in the pre-determined set of downlink subframes associated withsubframe n, the pre-determined set comprising M elements indexedaccording to k₀, k₁, . . . , k_(M-1), and wherein determining theresource index comprises calculating:n _(PUCCHi) ⁽¹⁾ =i·N _(q) ^(eCCE) +n _(eCCE,i) +N _(UE-PUCCH) ^((q))where n_(eCCE,i) is the lowest control channel element index of thereceived DCI and N_(q) ^(eCCE) is the number of control channel elementsin downlink control channel resource set q, wherein the resource indexis derived from n_(PUCCHi) ⁽¹⁾.
 4. A wireless device configured foroperation in a wireless communication network and comprising acommunication interface configured for communicating with one or morenetwork nodes in the wireless communication network and adapted toreceive downlink control information via a downlink control channel in adownlink subframe, the received downlink control channel scheduling adownlink shared channel transmission to the wireless device, and one ormore processing circuits configured to control the communicationinterface, wherein the processing circuits are adapted to: determine aresource index for an uplink control channel resource based on adevice-specific offset value previously signaled to the wireless deviceand an index i, wherein the index i identifies the downlink subframe ina pre-determined set of one or more downlink subframes associated withan uplink subframe, wherein said determining is according to a formulathat results in a sequential allocation of uplink control channelresources in the uplink subframe with respect to the downlink subframesassociated with the uplink subframe, for each of a plurality of sets ofdownlink control channel resources; and control the communicationinterface to transmit hybrid automatic-repeat-request (HARD) feedback inthe uplink subframe, using an uplink control channel resourcecorresponding to the resource index.
 5. The wireless device of claim 4,wherein the processing circuit is configured to determine the resourceindex for the uplink control channel resource based on the sum of (i)the lowest control channel element of the received DCI, (ii) thedevice-specific offset value previously signaled to the wireless device,and (iii) the product of the index i and the number of control channelelements in a set of downlink control channel resources that includesthose downlink control channel resources used by the received downlinkcontrol channel.
 6. The wireless device of claim 5, wherein the set ofdownlink control channel resources is set q of a plurality of sets ofdownlink control channel resources, wherein the uplink subframe issubframe n and the downlink subframe is subframe n-k_(i), where k_(i) isthe i-th element in the pre-determined set of downlink subframesassociated with subframe n, the pre-determined set comprising M elementsindexed according to k₀, k₁, . . . , k_(M-1), and wherein determiningthe resource index comprises calculating:n _(PUCCHi) ⁽¹⁾ =i·N _(q) ^(eCCE) +n _(eCCE,i) +N _(UE-PUCCH) ^((q)),where n_(eCCE,i) is the lowest control channel element index of thereceived DCI and N_(q) ^(eCCE) is the number of control channel elementsin downlink control channel resource set q, wherein the resource indexis derived from n_(PUCCHi) ⁽¹⁾.
 7. A method in a network node operatingin a wireless communication network configured for time-divisionduplexing (TDD) operation, said method comprising: transmitting downlinkcontrol information (DCI) to a wireless device via a downlink controlchannel in a downlink subframe, the transmitted downlink control channelscheduling a downlink shared channel transmission to the wirelessdevice; determining a resource index for an uplink control channelresource based on a device-specific offset value previously signaled tothe wireless device and an index i, wherein the index i identifies thedownlink subframe in a pre-determined set of one or more downlinksubframes associated with an uplink subframe, wherein said determiningis according to a formula that results in a sequential allocation ofuplink control channel resources in the uplink subframe with respect tothe downlink subframes associated with the uplink subframe, for each ofa plurality of sets of downlink control channel resources; and receivinghybrid automatic-repeat-request (HARQ) feedback from the wireless devicein the uplink subframe, using an uplink control channel resourcecorresponding to the resource index.
 8. The method of claim 7, whereindetermining the resource index for the uplink control channel resourcecomprises determining the resource index based on the sum of (i) thelowest control channel element of the received DCI, (ii) thedevice-specific offset value previously signaled to the wireless device,and (iii) the product of the index i and the number of control channelelements in a set of downlink control channel resources that includesthose downlink control channel resources used by the transmitteddownlink control channel.
 9. The method of claim 8, wherein the set ofdownlink control channel resources is set q of a plurality of sets ofdownlink control channel resources, wherein the uplink subframe issubframe n and the downlink subframe is subframe n-k_(i), where k_(i) isthe i-th element in the pre-determined set of downlink subframesassociated with subframe n, the pre-determined set comprising M elementsindexed according to k₀, k₁, . . . , k_(M-1), and wherein determiningthe resource index comprises calculating:n _(PUCCHi) ⁽¹⁾ =i·N _(q) ^(eCCE) +n _(eCCE,i) +N _(UE-PUCCH) ^((q)),where n_(eCCE,i) is the lowest control channel element index of thereceived DCI and N_(q) ^(eCCE) is the number of control channel elementsin downlink control channel resource set q, wherein the resource indexis derived from n_(PUCCH,i) ⁽¹⁾.
 10. A network node configured foroperation in a wireless communication network and comprising: acommunication interface configured for communicating with one or morewireless devices in the wireless communication network and adapted totransmit downlink control information (DCI) to a wireless device via adownlink control channel in a downlink subframe, the transmitteddownlink control channel scheduling a downlink shared channeltransmission to the wireless device, and one or more processing circuitsconfigured to control the communication interface, wherein theprocessing circuits are adapted to: determine a resource index for anuplink control channel resource based on a device-specific offset valuepreviously signaled to the wireless device and an index i, wherein theindex i identifies the downlink subframe in a pre-determined set of oneor more downlink subframes associated with an uplink subframe, whereinsaid determining is according to a formula that results in a sequentialallocation of uplink control channel resources in the uplink subframewith respect to the downlink subframes associated with the uplinksubframe, for each of a plurality of sets of downlink control channelresources; and, using the communication interface, receive hybridautomatic-repeat-request (HARQ) feedback in the uplink subframe, usingan uplink control channel resource corresponding to the resource index.11. The network node of claim 10, wherein the processing circuit isconfigured to determine the resource index for the uplink controlchannel resource based on the sum of (i) the lowest control channelelement of the received DCI, (ii) the device-specific offset valuepreviously signaled to the wireless device, and (iii) the product of theindex i and the number of control channel elements in a set of downlinkcontrol channel resources that includes those downlink control channelresources used by the transmitted downlink control channel.
 12. Thenetwork node of claim 11, wherein the set of downlink control channelresources is set q of a plurality of sets of downlink control channelresources, wherein the uplink subframe is subframe n and the downlinksubframe is subframe n-k_(i), where k_(i) is the i-th element in thepre-determined set of downlink subframes associated with subframe n, thepre-determined set comprising M elements indexed according to k₀, k₁, .. . , k_(M-1), and wherein determining the resource index comprisescalculating:n _(PUCCHi) ⁽¹⁾ =i·N _(q) ^(eCCE) +n _(eCCE,i) +N _(UE-PUCCH) ^((q)),where n_(eCCE,i) is the lowest control channel element index of thereceived DCI and N_(q) ^(eCCE) is the number of control channel elementsin downlink control channel resource set q, wherein the resource indexis derived from n_(PUCCHi) ⁽¹⁾.